The need to interface between a power source and loads to be powered has always been basic to applied electricity. The interface has consisted of a power connector for receiving incoming power via a mating connector, a fuse, and an output connector with cabling for routing power to loads.
The line of demarcation, the point along which the power connector is located, is the physical boundary of the assembly or subassembly. A system may have one or more power connector locations along its physical boundaries. Each point utilizes fuses, output connectors, and cabling as mentioned above.
The trend in recent decades has been toward physical equipments and components of increasingly smaller physical size. The result of this for power cabling and fusing has been the need for smaller components and the need to assemble and work with them in smaller physical spaces.
In addition, equipment reliability is of increased importance as systems grow in complexity. Reliability is enhanced if there are fewer points of connection in the power cabling assembly, and if there are fewer connections to be made within the power cabling after installation.